Driveline assemblies are a type of power take off assembly that transfers torque loads from a driving member to a driven member. The driveline assembly usually has a universal joint at each end. The typical cardan type universal joint is basically made up of two yokes each connected to a single center cross with four needle bearings. A fixed driveline assembly is used in applications where the required length of assembly does not vary such as power steering unit. A slip type or telescoping assembly is designed for applications in which the length of the assembly may vary during its normal operation because of application movement or function such as driveline connections between tandem drive axles for truck and tractor applications. Typical inter-axle slip type driveline assemblies can operate up to a 45.degree. angle and can have length variations in excess of 12 inches.
The slip type assembly is generally of a sliding spline design. A yoke shaft is fitted into a slip yoke with an internal spline that generally mates with the external spline of the yoke shaft. Universal joint assemblies are attached to each yoke completing the assembly. The splined cavity within the slip yoke generally contains lubricants and is sealed by a plug and a seal which keeps the lubricants in and contaminants out.
The seal is generally one of two types: multi-component or one piece. With multiple-component seals, one or more split washers with internal splines are positioned over the end of the slip yoke and held in place by a threaded metal dust cap. The washer sets are usually of metal and cork or nylon and felt construction. With single piece construction, the dust cap is generally rubber with an internal thread that allows it to be screwed over the end of a slip yoke with matching external threads. The outer surface of the threaded portion of the seal is generally bonded to a metal band that helps maintain the overall seal geometry and prevents thread deformation.
In both arrangements there must be internal threads on the dust seal and corresponding external threads on the slip yoke. These threads on the slip yoke are susceptible to damage in handling and tight controls are required in processing.